Dulles rail tunnel completed

The Dulles Corridor Metrorail Project in northern Virginia has completed the tunnel that will carry the future rail line under a portion of Tysons Corner, Va., just outside of Washington, D.C.

"The completion of the mining and concrete operations for the twin bores of the tunnel marks a significant accomplishment given that the section was considered the most complex engineering and construction phase of the project due to the tunnel's location," said George Morschauser, the project's executive director.

Construction of the tunnel began in October 2009 and was completed two months ahead of schedule and under budget in November 2011. The tunnel was constructed using the technique called the New Austrian Tunneling Method. Crews would excavate a short section and then cover it with an initial lining of shotcrete. This process was repeated multiple times for both the inbound and outbound tunnels, which are each 1,700 feet.

During construction of the tunnel, crews removed approximately 100,000 cubic yards of earth for the openings; sprayed 25,000 cubic yards of shotcrete for the initial liner and applied 18,000 cubic yards of concrete for the final liner. With the tunneling complete, crews will now install the rail.